A standard motor-vehicle door latch has a housing mounted on the door edge and formed with a recess into which is engageable a bolt projecting from the respective door post. A fork is pivotal in the housing between a latching position engaging around the bolt and holding it solidly in the recess and a freeing position permitting the bolt to enter and leave the recess. A latch pawl engageable with the fork can hold it in the latched position. The latch pawl in turn is typically spring loaded and can be controlled via appropriate levers both from an inside door handle and an outside door handle, either of which can therefore operate the latch to allow the door to be opened.
In addition the door can be locked by means of a button or lever inside the door and a key cylinder outside the door, and also frequently by an actuator operated by a central lock system. When locked the outside door handle is either impeded from moving so it cannot move the latch pawl, or it is decoupled from the latch pawl so its actuation is ineffective.
In a standard lock system the inner door handle and inner lock button or lever remain effective even when the door is locked and the outside handle does not work. In an antitheft system as described in U.S. patent application Nos. 389,652 now patent No. 4,974,886, issued Dec. 4, 1990 and 596,926 respectively filed Aug. 4, 1989 and Oct. 12, 1990 there is, in addition to the locked and unlocked conditions of the latch, an antitheft mode or position in which the latch cannot be opened by either of the door handles and in which the inside lock element is also ineffective to unlock the door. Thus when in the antitheft position a would-be thief cannot even open the door by forcing the window and operating the door from inside.
As described in commonly owned patent application 389,834 now patent No. 4,978,154, issued Dec. 18. 1990, filed Aug. 4, 1990 the remotely operated antitheft mechanism uncouples the inside door-locking element from the door-opening mechanism when in the antitheft position, a substantial improvement on the earlier known system of the type described in U.S. Pat. No. 4,669,283 where the antilock mechanism merely blocks actuation of the inside door-locking element.
The main disadvantage of these systems is that when they are to be applied to motor vehicles that are also offered without antitheft or remote-actuator systems, it is necessary for the manufacturer or assembler to stock two entirely different set of locks. It is impossible to merely leave out elements of the antitheft elements for use in a system not to be thus equipped, as that would eliminate elements necessary to couple the lock-operating and -actuating elements to each other.